Height control valve for air spring with end piston-boot operated

ABSTRACT

A height control valve assembly for a vehicle leveling system includes an air spring having a resilient rolling lobe which rolls onto and off of a bell-shaped surface of an air spring piston. A height control valve in the piston is operated by the air spring lobe as it rolls onto and off of the piston to control the amount of air pressure within the air spring.

nited. States Patent [191 Owen [ Feb. 5, 1974 HEIGHT CONTROL VALVE FORAIR SPRING WITH END PISTON-BOOT OPERATED [75] Inventor: Robert E. Owen,Grand Blanc,

Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Nov. 17, 1972 [21] Appl. No.: 307,218

[52] US. Cl. 267/65 B [51] Int. Cl. F16g 5/00 [58] Field of Search....267/65 B, 65 A, 65 R, 64 R, '267/64 B [56] References Cited UNITEDSTATES PATENTS 2,916,298 12/1959 McMullin 267/65 B 3,074,709 l/l963Ballard et al 267/65 B Primary Examiner-James B. Marbert Attorney,Agent, or Firm J. C. Evans 5 ABSTRACT A height control valve assemblyfor a vehicle leveling system includes an air spring having a resilientrolling lobe which rolls onto and off of a bell-shaped surface of' anair spring piston. A height control valve in the pistonis operated bythe air spring lobe as it rolls onto and off of the piston to controlthe amount of air pressure within the air spring.

5 Claims, 4 Drawing Figures HEIGHT CONTROL VALVE FOR AIR SPRING WITH ENDPISTON-BOOT OPERATED This invention relates to height control valveassemblies for vehicle leveling systems and more particularly to heightcontrol valves carried on one of a pair of relatively moving members ina vehicle leveling spring unit which is operated by the other relativelymoving member to control air pressure within the air spring unit.

Vehicle leveling systems include valve components therein operated inresponse to changes in load on the vehicle chassis to regulate the airpressure within an air spring leveler unit of the system so as tomaintain a predetermined height relationship between the sprung and theunsprung mass of the vehicle.

In some cases, the valve is carried as part of the leveler unit. In thepast, the valve has been carried on a portion of the leveler unit andhas been operated by another portion of the leveler unit which movesrelative to the valve in accordance with changes in the height of thevehicle chassis with respect to unsprung mass portions of a vehiclesuspension. In certain arrangements, the valve is located internally ofthe leveler component. Usually, in these cases a separate lever operatoris utilized to control the valve. In other versions, a rolling lobe ofan air spring is used to open and close an orifice opening to obtain thevalve control at a point external of the leveler unit.

An object of the present invention is to provide a simplified heightcontrol valve assembly for use on air springs of the type including anelongated sleeve having a rolling lobe on at least one end thereof whichis connected to a piston that, along with the sleeve, forms apressurizable air chamber for varying the height relationship of the airspring unit and wherein a sealed valve is located within the piston andoperated by rolling action of the lobe onto and off of the air piston toregulate pressurization of the air spring.

Still another object of the present invention is to improve the controlof pressure within an air spring of the type including a diaphragmhaving a lobe portion thereon and a piston defining a pressurizablechamber by the provision of valve means carried by the piston and sealedinternally thereof and wherein the seal means for the valve is locatedin operative relationship with the lobe of the diaphragm and operatedthereby as the lobe rolls on and off the piston to operate the valveinto opened and closed positions for controlling the pressure level inthe pressurizable chamber of the lev' eler unit.

Yet another object of the present invention is to provide an improvedheight control arrangement for use in air spring assemblies of the typehaving a lobed diaphragm and a piston for forming a pressurizable airchamber by the provision of a simplified on/off valve assembly supportedby the piston internally thereof and a seal for excluding debris fromexteriorly of the air unit from the valve assembly with the seal meansbeing formed in part by a bulked end thereon with a curve surfaceextending slightly beyond the outer surface of the piston, operativelyengaged by a curved portion of the lobe of the diaphragm as it moves onand off of the outer surface of the piston to produce axial movementofthe seal member which positions the valve in a closed position when thelobe is located on the piston and which positions the valve'open whenthe spring lobe is off the piston.

These and other objects of the present invention are attained in oneworking version which includes an air spring unit having an elongatedsleeve portion having a length in excess of the diameter thereof withlobes formed on each end thereof by tapered ends of the sleeve. Each ofthe lobes are fastened to a piston having a bell-shaped outer surfaceconfiguration. The pistons and sleeve form a pressurizable air chamber.One of the pistons has an inlet recess therein which communicates with atransverse bore formed through the piston through the bell-shapedsurface thereon. The bore has a valve seat therein. An elongated stem islocated within the bore and supports a valving element on one endthereof whichis moved into and out of engagement with the valve seat. Aseal member closes the outer end of the bore and is located in overlyingrelationship to the end of the elongated stem. It includes a curvilinearsurface thereon located exteriorly of the piston at a point to beengaged by the lobe of the spring as it moves onto and off of the pistonin accordance with distance between the pistons. When a vehicle isslightly loaded, the pistons are moved apart from one another so as tocause the lobe to move off the bell-shaped surface of the piston andaway from the seal member allowing the elongated stem to move in adirection to shift the valving element from a sealed relationship withthe valve seat. When the vehicle is heavily loaded, the lobe of thesleeve will move onto the bell-shaped surface and will engage the sealelement to move the elongated stem to shift the valving element into aclosed sealed relationship with the valve seat.

Further objects and advantages of the present inven tion will beapparent from the following description, reference being had to theaccompanying drawings wherein a preferred embodiment of the presentinvention is clearly shown.

IN THE DRAWINGS:

FIG. 1 is a fragmentary view of a vehicle leveling system including thepresent invention;

FIG. 2 is an enlarged sectional view through lines 2-2 of FIG. lllooking in the direction of the arrows; and

FIG. 3 is an enlarged fragmentary sectional view of the presentinvention; and

FIG. 4 is a further enlargement of FIG. 3.

Referring now to the drawings, in FIG. 1, a portion of a rear suspensionleveling system 10 is illustrated. It includes an air spring assembly 12having an upper piston 14 thereof connected to a cross frame member 16on the rear suspension of a vehicle. A lower piston 18 of the air springassembly 12 is supported by a ledge 20 on a differential housing 22.

The air spring assembly further includes an elongated diaphragm sleeve24 having a rolling lobe 26 at the upper end and a like rolling lobe 28at the bottom thereof.

The air spring assembly 12 serves as a load-leveling component in theleveling system 10. It is operatively associated with an air supply'system 30 including an air inlet 32 connected to the open end of adessicant tank 34. Air flows through the dessicant tank to a fitting 36thereon that connects to one end of a supply conduit 38 having theopposite end thereof connected to a compressor inlet fitting 40. Thecompressor also has an outlet 42 connected to an inlet end of a pressureconduit 44. The opposite end of pressure conduit-44 is connected to afitting 46 that is threadably received in a base 48 of the lower piston18.

The piston includes a stepped bore50 on the interior thereof whichcommunicates the fitting 46 with a pressurizable air chamber 52 formedby the upper piston 14, the elongated diaphragm sleeve 24 and the lowerpiston 18. The end of the upper lobe 26 is located within a groovedcontinuously formed peripheral surface 54 on a small diameter end 56 ofthe upper piston 14. It is held in sealing engagement thereon by a clampring 58. Likewise, the end of the lower lobe 28 is located on a groovedcontinuously formed peripheral surface 60 formed on the inner end62 ofthe lower piston 18. It is held in sealing engagement with the surface60 by means of a clamp ring 64.

Air flow from the chamber is under the control of an improved heightcontrol valve assembly 65 which includes a lateral bore 66 formedthrough the piston 18 including an outwardly located enlarged diameterportion 68 and an inwardly located shoulder 70 that defines a supportfor an air spring orifice and seat member 72. More particularly, themember 72 includes a peripheral groove 74 which fits over the shoulder70 of the piston bore. It has a head portion 76 that overlies theshoulder 70. The head portion has an internal groove 78 in which isseated an orifice plate 80 for regulating the rate of air flow from thepressurizable air chamber 52 into the lateral bore 66. Within thelateral bore 66 is located an elongated valve stem 82 having a hexagonalcross-section defining a peripheral surface spaced from the bore 66 todefine a passageway 84 between the stem 82 and the bore 66.

The stem 82 is undercut at 86 to define a spring seat 88 in engagementwith one end ofa minimum pressure retention spring 90. It has theopposite end thereof sup ported by a stop element 92 seated on the innerend of the enlarged bore portion 68. The minimum pressure retentionspring yields against the buildup of pressure within the chamber 52above a predetermined minimum-pressure that is required to maintain ashape to the lobes 26, 28 of the diaphragm 24 under low load conditionsso that they will freely roll on and off of the outer surfaces of thepistons 14, 18. The spring 90 urges a valving element 94 carried on theend of the stem against an annular valve seat surface 96 on member 72 toclose a flow passageway 98 through the member 72. Exhaust flow from thevalve assembly 64 is through the passageway 84 and an exhaust passageway100 in piston 18 that intersects the bore 66 outwardly of the seat 96.The exhaust passageway 100 has a tube connector fitting 102 threadablyreceived therein. It in turn is connected to an exhaust line or conduit104 which is connected to a fitting 36 on the dessicant tank 34.

One feature of the present invention is that the working components ofthe valve are located completely within the body of the piston 18. Theinternal location is sealed by means of a boot member 106 which has anannular inner end 107 thereon seated within the large diameter portion68 against the stop 92. The boot end 107 is securedin place by means ofa retaining washer 108. Member 106 further includes an inwardly formedmidportion 110 having an annular internal surface 112 located in closesurrounding relationship with an outward extension 114 of the stem 82which is located within the large diameter bore 68. The terminus ofextension 114 is spaced with respect to an inner surface 116 of aspherical bulbed end portion 118 that has a curved outer surface 120located slightly outwardly of the outer surface of the piston 18. In theillustrated arrangement the piston 18 has a bell-shaped curved outersurface 122 onto which the lower lobe 28 of the air spring diaphragm 24rolls on and off during vehicle leveling operations.

When in the position shown in FIG. 2, an inner wall 124 of the lobe 28overlies the bulbed end 118 of the boot and the midportion 110 of theboot yields axially to cause the inner surface 116 of the boot 106 toengage the extension 114 to shift the valve stem 82 so as to sealinglypress the valving element 94 against the seat 96 so as to holdsubstantial pressures within the air chamber 52.

The boot 1 14 in addition to transferring the action of the rolling lobe28 against the stem serves to completely seal the internally locatedvalve components against dust, moisture and other debris typically foundoutside of an air spring unit of the type illustrated. The conditionshown in FIG. 2 is caused when additional load is placed on the vehiclechassis. This will cause a pair of rear, primary suspension springs tobe compressed. One of the springs is shown at 126 in FIG. 1. As in thecase of both of the springs, it has the upper end thereof carried on aspring seat 128 at the rear side of the cross member 16. The lower endthereof is supported on a bracket (not shown) supported by an axlehousing 130. The movement between the chassis and the axle housing 130is controlled by a pair of upper control arms 132, 134 of a conventionaltype. Additionally, the suspension includes a pair of lower controlarms, one of which is shown at 136. These components are conventionalcomponents found on four link type rear suspensions and form no part ofthe present invention.

When load is removed from the vehicle chassis, the springs will move thechassis frame away from the axle housing 130. This will cause thepistons 16 and 18 to be separated from one another until the lower lobe28 moves off of the bell-shaped surface 122. The unit then assumes theoperative relationship in FIG. 3 with the boot 106 extending from themidpoint 110 thereof to locate the inner surface 116 of the bulbed end118 away from the stem extension 114. At this point, only the force ofthe minimum pressure retention spring acts on the stem 84. Accordingly,pressure within the pressurizable chamber 52 presses against the valvingelement 94 causing it to move to the open position shown in FIG. 3 andair is exhausted from the bore 50 through the exhaust passageway 100thence through the exhaust conduit 104- and the dessicant tank 34 thencethrough the fitting 32 to atmosphere.

The aforedescribed valving assembly 65 in addition to being internallylocated and sealed against outside influences is readily replaced fromexteriorly of the leveler unit 12.

In the illustrated arrangement, it controls the height relationshipbetween the sprung and unsprung mass portion to within one-fourth of thedistance which is established as a normal predetermined heightrelationship therebetween.

It is operative to control pressures from a minimum pressure level of 10psig when the valve is in the open position with only the minimumpressure retention valve operative to a pressure of 60 psig when thevalve is closed as shown in FIG. 2. t

While the embodiments of the present invention, as

herein disclosed, constitute a preferred form, it is to be understoodthat other forms might be adopted.

What is claimed is as follows:

1. A control valve assembly for a vehicle leveling sys tem comprising anair spring piston having a base por tion adapted to be connected to afirst suspension com ponent, said piston including an inner end portionthereon of a first diameter, an outer surface on said piston including areduced diameter at one end thereof anda progressively increasingdiameter at the opposite end thereof, a tubular air spring sleeveincluding a rolling lobe portion, an end on said rolling lobe overlyingsaid small diameter end of said outer piston, means for holding saidlobe end portion in sealing engagement with said piston, said rollinglobe including an inner wall portion movable onto and from said outersurface of said piston, means including said sleeve and said piston forforming a pressurizable air chamber for varying the pressurization ofsaid air sleeve to produce a reaction against said piston member toproduce a supplemental spring force, a bore extending through saidpiston from said outer surface thereof into said pressurizable chamber,a valve seat formed in alignment with said bore, a valve stem having avalving element thereon located in alignment with said seat adapted tobe moved into opened and closed relationship with said seat, said stemincluding a plunger on one end thereof directed outwardly of said bore,means forming an outlet pas sageway in communication with said boreadapted to be connected to a fluid supply system for said air spring, aseal boot supported by said piston having an inner surface thereon inengagement with said plunger and including an outer surface portionthereon extending outwardly of said piston at the small diameter end ofsaid outer piston surface, said rolling lobe of said air sleeve havingan inner wall portion thereon movable onto and off of said outer pistonsurface engageable with said outer surface of said boot to exert aninward pressure on said stem so as to maintain said valving elementtightly closed against said valve seat to trap air within said airchamber to increase the air pressure therein, said air spring sleeveresponding to a reduction of vehicle load thereon to cause the innerwall of said rolling lobe to roll off said outer piston surface and awayfrom said outer boot surface to reduce the inward exertion of pressureon said valving element, said valving element responding to apredetermined pressure thereon when said rolling lobe is no longerpressed against said boot to cause said valve stem to move away fromsaid valve seat to leak air from said air chamber through said outletpassageway.

2. A control valve assembly for a vehicle leveling system comprising anair spring piston having a base portion adapted to be connected to afirst suspension component, said piston including an inner end portionthereon of a first diameter, a bell-shaped outer surface on said pistonincluding a reduced diameter at one end thereof and a progressivelyincreasing diameter at the opposite end thereof, a tubular air springsleeve includ ing a rolling lobe portion, an end on said rolling lobeoverlying said small diameter end of said outer piston, means forholding said lobe end portion in sealing engagement with said piston,said rolling lobe including an inner wall portion movable onto and fromsaid bellshaped surface of said piston, means including said sleeve andsaid piston for forming a pressurizable air chamber for varying thepressurization of said air sleeve to produce a reaction against saidpiston mem ber to produce a supplemental spring force, a bore extendingthrough said piston from said bell-shaped outer surface thereof intosaid pressurizable chamber, a valve seat formed in alignment with saidbore, a valve stem having a valving element thereon located in alignmentwith said seat adapted to be moved into opened and closed relationshipwith said seat, means including a minimum pressure retention springbiasing said stem to move said sealing element into a closed positionagainst said seat, said stem including a plunger on one end thereofdirected outwardly of said bore, an outlet passageway in said boreadapted to be connected to a fluid supply system for said air spring, aseal boot supported by said piston having an inner surface thereon inengagement with said plunger and including an outer surface portionthereon extending outwardly of said piston at the small diameter end ofsaid bell-shaped outer surface, said rolling lobe of said air sleevehaving an inner wall portion thereon movable onto and off of saidbellshaped surface engageable with said outer surface of said boot forsupplementing the spring bias of said minimum pressure retention springto exert an inward pres sure on said stem so as to maintain said valvingelement tightly closed against said valve seat to trap air within saidair chamber to increase the air pressure therein, said air spring sleeveresponding to a reduction of vehicle load thereon to cause the innerwall of said rolling lobe to roll off said outer bell-shaped surface andaway from said outer boot surface to reduce the pressure on said valvingelement, said valving element responding to a predetermined pressurethereon when said rolling lobe is no longer against said boot toovercome said minimum pressure retention spring and to cause said valvestem to move away from said valve seat to leak air from said air chamberthrough said exhaust passageway in said air spring piston.

3. An air spring assembly comprising a tubular air spring sleeve, meansfor closing one end of said tubular air spring sleeve, a rolling lobe onthe other end of said sleeve, said rolling lobe including an inner walland an end portion thereon, a piston having a small diameter inner endthereon located within the end of said rolling lobe, means for sealingsaid pistonand sleeve ends together, an outer surface on said pistonhaving a smaller diameter adjacent said small diameter end of saidpiston and a progressively increasing diameter, said rolling lobeincluding an inner wall movable onto and off of said outer pistonsurface and a curved portion, said piston and said sleeve forming apressurizable air chamber adapted to be inflated to vary the reaction onsaid piston for producing a resultant force between the ends of saidtubular sleeve, said piston including a bore therethrough extending fromsaid outer piston surface and into said pressurizable air chamber, anelongated valve stem located within said bore, a valving element carriedon one end of said stem, means defining a valve seat in said bore inalignment with said valving element, means forming an exhaust passagewayin communication with said bore, a boot including a base portion locatedwithin said bore, means for holding said boot end in sealing engagementwith said bore, said boot including an inwardly pinched midportionthereon and a bulbed end having an inner surface engageable with theoutermost end of said valve stem and an outer surface with curvedsegments thereon located outwardly of said piston beyond said outersurface thereon, said outer surface curved segments being engageablewith the curved portion of said rolling lobe of said sleeve as saidsleeve lobe passes onto and off. of said piston to move said bootinwardly of said valve bore, said inner surface of said boot engagingsaid valve stem when said rolling lobe is in contact therewith to moveit inwardly of said bore to cause said valving element to move intosealed engagement with said valve seat, said inwardly directedmidportion of said boot located in close spaced relationship to saidstem and movable with respect thereto upon valve closing movement ofsaid stem to guide said stem linearly of said valve stem bore duringvalve closing and opening movements, said stem being moved away fromsaid seat by pressure on said valving element when said lobe is out ofengagement with said bulbed end to cause air to leak from said sleeveinto said exhaust passageway means.

4. An air spring assembly comprising a tubular air spring sleeve, meansfor closing one end of said tubular air spring sleeve, a rolling lobe onthe other end of said sleeve, said rolling lobe including an inner walland an end portion thereon, a piston having a small diameter inner endthereon located within the end of said rolling lobe, means for sealingsaid piston and sleeve ends together, an outer surface on said pistonhaving a smaller diameter adjacent said small diameter end of saidpiston and a progressively increasing diameter, said rolling lobeincluding an inner wall movable onto and off of said outer pistonsurface and a curved portion, said piston and said sleeve forming apress'urizable air chamber adapted to be inflated to vary the reactionon said piston for producing a resultant force between the ends of saidtubular sleeve, said piston including a bore therethrough extending fromsaid outer piston surface and into said pressurizable air chamber, anelongated valve stem located within said bore having the walls thereofspaced from said wall to form an axial opening therebetween, a valvingelement carried on one end of said stem, means defining a valve seat insaid bore in alignment with said valving element, minimum pressureretention spring means acting on said stem for holding said valvingelement against said seat to trap a predetermined minimum pressurewithin said air chamber, means forming an exhaust passageway incommunication with said axial passageway, a boot including a baseportion located within said bore, means for holding said boot end insealing engagement with said bore, said boot including an inwardlypinched midportion thereon and a bulbed end having an inner surfaceengageable with the outermost end of said valve stem and an outersurface with curved segments thereon located outwardly of said pistonbeyond said outer surface thereon, said outer surface curved segmentsbeing engageable with a curved portion of said rolling lobe of i saidsleeve as said sleeve lobe passes onto and off of said piston surface tomove said boot inwardly of said valve bore, said inner surface of saidboot engaging said valve stem when said rolling lobe is in contacttherewith to move it inwardly of said bore to cause said valving elementto move into sealed engagement with said valve seat, said inwardlydirected midportion of said boot located in close spaced relationship tosaid stem and movable with respect thereto upon valve closing movementof said .stem to guide said stem linearly of said valve stem bore duringvalve closing and opening movements, said stem being moved away fromsaid seat by pressure on said valving element when said lobe is out ofengagement with said bulbed end to cause air to leak from said sleeveinto said exhaust passageway means.

5. An air spring assembly comprising a tubular air spring sleeve, meansfor closing one end of said tubular air spring sleeve, a rolling lobe onthe other end of said sleeve, said rolling lobe including an inner walland an end portion thereon, a piston having a small diameter inner endthereon located within the end of said rolling lobe, means for sealingsaid piston and sleeve ends to gether, an outer surface on said pistonhaving a smaller diameter adjacent said small diameter end of saidpiston and a progressively increasing diameter, said rolling lobeincluding an inner wall movable onto and off of said outer pistonsurface and a curved portion, said piston and said sleeve forming apressurizable air chamber adapted to be inflated to vary the reaction onsaid piston for producing a resultant force between the ends of saidtubular sleeve, said piston including a bore therethrough extending fromsaid outer piston surface and into said pressurizable air chamber, meansforming an exhaust passageway in communication with said bore, meansdefining a valve seat in said bore, valving means for opening andclosing said valve seat, said valve means including an operator withcurved segments thereon located outwardly of said piston beyond saidouter surface thereon, said outer surface curved segments beingengageable with the curvedportion of said rolling lobe of said sleeve assaid sleeve lobe passes onto and off of said piston to move saidoperator inwardly of said valve bore to close said valve seat, saidvalve means being moved away from said seat by pressure thereon whensaid lobe is out of engagement with said operator to cause air to leakfrom said sleeve into said exhaust passageway means.

1. A control valve assembly for a vehicle leveling system comprising anair spring piston having a base portion adapted to be connected to afirst suspension component, said piston including an inner end portionthereon of a first diameter, an outer surface on said piston including areduced diameter at one end thereof and a progressively increasingdiameter at the opposite end thereof, a tubular air spring sleeveincluding a rolling lobe portion, an end on said rolling lobe overlyingsaid small diameter end of said outer piston, means for holding saidlobe end portion in sealing engagement with said piston, said rollinglobe including an inner wall portion movable onto and from said outersurface of said piston, means including said sleeve and said piston forforming a pressurizable air chamber for varying the pressurization ofsaid air sleeve to produce a reaction against said piston member toproduce a supplemental spring force, a bore extending through saidpiston from said outer surface thereof into said pressurizable chamber,a valve seat formed in alignment with said bore, a valve stem having avalving element thereon located in alignment with said seat adapted tobe moved into opened and closed relationship with said seat, said stemincluding a plunger on one end thereof directed outwardly of said bore,means forming an outlet passageway in communication with said boreaDapted to be connected to a fluid supply system for said air spring, aseal boot supported by said piston having an inner surface thereon inengagement with said plunger and including an outer surface portionthereon extending outwardly of said piston at the small diameter end ofsaid outer piston surface, said rolling lobe of said air sleeve havingan inner wall portion thereon movable onto and off of said outer pistonsurface engageable with said outer surface of said boot to exert aninward pressure on said stem so as to maintain said valving elementtightly closed against said valve seat to trap air within said airchamber to increase the air pressure therein, said air spring sleeveresponding to a reduction of vehicle load thereon to cause the innerwall of said rolling lobe to roll off said outer piston surface and awayfrom said outer boot surface to reduce the inward exertion of pressureon said valving element, said valving element responding to apredetermined pressure thereon when said rolling lobe is no longerpressed against said boot to cause said valve stem to move away fromsaid valve seat to leak air from said air chamber through said outletpassageway.
 2. A control valve assembly for a vehicle leveling systemcomprising an air spring piston having a base portion adapted to beconnected to a first suspension component, said piston including aninner end portion thereon of a first diameter, a bell-shaped outersurface on said piston including a reduced diameter at one end thereofand a progressively increasing diameter at the opposite end thereof, atubular air spring sleeve including a rolling lobe portion, an end onsaid rolling lobe overlying said small diameter end of said outerpiston, means for holding said lobe end portion in sealing engagementwith said piston, said rolling lobe including an inner wall portionmovable onto and from said bell-shaped surface of said piston, meansincluding said sleeve and said piston for forming a pressurizable airchamber for varying the pressurization of said air sleeve to produce areaction against said piston member to produce a supplemental springforce, a bore extending through said piston from said bell-shaped outersurface thereof into said pressurizable chamber, a valve seat formed inalignment with said bore, a valve stem having a valving element thereonlocated in alignment with said seat adapted to be moved into opened andclosed relationship with said seat, means including a minimum pressureretention spring biasing said stem to move said sealing element into aclosed position against said seat, said stem including a plunger on oneend thereof directed outwardly of said bore, an outlet passageway insaid bore adapted to be connected to a fluid supply system for said airspring, a seal boot supported by said piston having an inner surfacethereon in engagement with said plunger and including an outer surfaceportion thereon extending outwardly of said piston at the small diameterend of said bell-shaped outer surface, said rolling lobe of said airsleeve having an inner wall portion thereon movable onto and off of saidbell-shaped surface engageable with said outer surface of said boot forsupplementing the spring bias of said minimum pressure retention springto exert an inward pressure on said stem so as to maintain said valvingelement tightly closed against said valve seat to trap air within saidair chamber to increase the air pressure therein, said air spring sleeveresponding to a reduction of vehicle load thereon to cause the innerwall of said rolling lobe to roll off said outer bell-shaped surface andaway from said outer boot surface to reduce the pressure on said valvingelement, said valving element responding to a predetermined pressurethereon when said rolling lobe is no longer against said boot toovercome said minimum pressure retention spring and to cause said valvestem to move away from said valve seat to leak air from said air chamberthrough said exhaust passageway in said air spring pistoN.
 3. An airspring assembly comprising a tubular air spring sleeve, means forclosing one end of said tubular air spring sleeve, a rolling lobe on theother end of said sleeve, said rolling lobe including an inner wall andan end portion thereon, a piston having a small diameter inner endthereon located within the end of said rolling lobe, means for sealingsaid piston and sleeve ends together, an outer surface on said pistonhaving a smaller diameter adjacent said small diameter end of saidpiston and a progressively increasing diameter, said rolling lobeincluding an inner wall movable onto and off of said outer pistonsurface and a curved portion, said piston and said sleeve forming apressurizable air chamber adapted to be inflated to vary the reaction onsaid piston for producing a resultant force between the ends of saidtubular sleeve, saId piston including a bore therethrough extending fromsaid outer piston surface and into said pressurizable air chamber, anelongated valve stem located within said bore, a valving element carriedon one end of said stem, means defining a valve seat in said bore inalignment with said valving element, means forming an exhaust passagewayin communication with said bore, a boot including a base portion locatedwithin said bore, means for holding said boot end in sealing engagementwith said bore, said boot including an inwardly pinched midportionthereon and a bulbed end having an inner surface engageable with theoutermost end of said valve stem and an outer surface with curvedsegments thereon located outwardly of said piston beyond said outersurface thereon, said outer surface curved segments being engageablewith the curved portion of said rolling lobe of said sleeve as saidsleeve lobe passes onto and off of said piston to move said bootinwardly of said valve bore, said inner surface of said boot engagingsaid valve stem when said rolling lobe is in contact therewith to moveit inwardly of said bore to cause said valving element to move intosealed engagement with said valve seat, said inwardly directedmidportion of said boot located in close spaced relationship to saidstem and movable with respect thereto upon valve closing movement ofsaid stem to guide said stem linearly of said valve stem bore duringvalve closing and opening movements, said stem being moved away fromsaid seat by pressure on said valving element when said lobe is out ofengagement with said bulbed end to cause air to leak from said sleeveinto said exhaust passageway means.
 4. An air spring assembly comprisinga tubular air spring sleeve, means for closing one end of said tubularair spring sleeve, a rolling lobe on the other end of said sleeve, saidrolling lobe including an inner wall and an end portion thereon, apiston having a small diameter inner end thereon located within the endof said rolling lobe, means for sealing said piston and sleeve endstogether, an outer surface on said piston having a smaller diameteradjacent said small diameter end of said piston and a progressivelyincreasing diameter, said rolling lobe including an inner wall movableonto and off of said outer piston surface and a curved portion, saidpiston and said sleeve forming a pressurizable air chamber adapted to beinflated to vary the reaction on said piston for producing a resultantforce between the ends of said tubular sleeve, said piston including abore therethrough extending from said outer piston surface and into saidpressurizable air chamber, an elongated valve stem located within saidbore having the walls thereof spaced from said wall to form an axialopening therebetween, a valving element carried on one end of said stem,means defining a valve seat in said bore in alignment with said valvingelement, minimum pressure retention spring means acting on said stem forholding said valving element against said seat to trap a predeterminedminimum pressure within said air chamber, means forming an exhaustpassageway in communication with said axial passagewaY, a boot includinga base portion located within said bore, means for holding said boot endin sealing engagement with said bore, said boot including an inwardlypinched midportion thereon and a bulbed end having an inner surfaceengageable with the outermost end of said valve stem and an outersurface with curved segments thereon located outwardly of said pistonbeyond said outer surface thereon, said outer surface curved segmentsbeing engageable with a curved portion of said rolling lobe of saidsleeve as said sleeve lobe passes onto and off of said piston surface tomove said boot inwardly of said valve bore, said inner surface of saidboot engaging said valve stem when said rolling lobe is in contacttherewith to move it inwardly of said bore to cause said valving elementto move into sealed engagement with said valve seat, said inwardlydirected midportion of said boot located in close spaced relationship tosaid stem and movable with respect thereto upon valve closing movementof said stem to guide said stem linearly of said valve stem bore duringvalve closing and opening movements, said stem being moved away fromsaid seat by pressure on said valving element when said lobe is out ofengagement with said bulbed end to cause air to leak from said sleeveinto said exhaust passageway means.
 5. An air spring assembly comprisinga tubular air spring sleeve, means for closing one end of said tubularair spring sleeve, a rolling lobe on the other end of said sleeve, saidrolling lobe including an inner wall and an end portion thereon, apiston having a small diameter inner end thereon located within the endof said rolling lobe, means for sealing said piston and sleeve endstogether, an outer surface on said piston having a smaller diameteradjacent said small diameter end of said piston and a progressivelyincreasing diameter, said rolling lobe including an inner wall movableonto and off of said outer piston surface and a curved portion, saidpiston and said sleeve forming a pressurizable air chamber adapted to beinflated to vary the reaction on said piston for producing a resultantforce between the ends of said tubular sleeve, said piston including abore therethrough extending from said outer piston surface and into saidpressurizable air chamber, means forming an exhaust passageway incommunication with said bore, means defining a valve seat in said bore,valving means for opening and closing said valve seat, said valve meansincluding an operator with curved segments thereon located outwardly ofsaid piston beyond said outer surface thereon, said outer surface curvedsegments being engageable with the curved portion of said rolling lobeof said sleeve as said sleeve lobe passes onto and off of said piston tomove said operator inwardly of said valve bore to close said valve seat,said valve means being moved away from said seat by pressure thereonwhen said lobe is out of engagement with said operator to cause air toleak from said sleeve into said exhaust passageway means.